Step 1: After fertilization, the corpus luteum continues to secrete high levels of progesterone.
Step 2: High progesterone levels maintain the endometrial lining of the uterus to support the developing fetus and inhibit the release of FSH and LH from the pituitary.
Step 3: This suppression prevents the maturation of new follicles and the shedding of the uterine lining, thereby ceasing the menstrual cycle for the duration of the pregnancy.